Conventionally, a charge device that performs a communication with a vehicle via a built-in communication line within a charge cable is known. The charge cable may also include a built-in power line to provide an electric power to the vehicle for charging a secondary battery of the vehicle.
For example, a device in a patent document 1 (i.e., Japanese Patent Laid-Open No. 2013-59176) performs a CPLT (Control Pilot Line Transmission) communication, via a communication line for an exchange of charge progress notices, notifying of charge procedures such as a connection of the charge cable, disconnection thereof, a completion of charge preparation, a start/end of charging, etc. In the present specification, a communication via communication line that is integrated with the power line in the charge cable, such as the CPLT communication for an exchange of the charge progress, is designated as a pilot communication. Further, in the disclosure of the patent document 1, it is described that the communication line used for the pilot communication is also used for an in-band communication by multiplexing an in-band signal.
The in-band communication may be performed by a more complex communication method than the pilot communication, such as an OFDM, for example, in addition to using a much higher frequency. For implementing such a complex communication method, a high processing capacity computer has to be used, in comparison to a communication circuit used for the pilot communication.
When a high processing capacity computer is used, the computer tends to suffer from noise in the in-band signal or other noise like factors, which results in frequent malfunctions of the computer. That is, when the in-band communication is required, the computer may not operate properly.